Accurate position information from the Global Positioning System (GPS) has been available for civilian use since 2000 when GPS “selective availability” was discontinued. GPS receivers for consumer use found their natural application first in car navigation. More recently, after further development and miniaturization of electronics, GPS chips have been integrated into smart-phone devices as well, potentially enabling personal navigation to become accessible in everyday and always-on use.
However, while GPS positioning systems typically perform well in outdoor environments, such systems often fail or provide degraded performance in indoor or urban canyon environments due to occlusion and multipath problems. For this reason, indoor navigation, while desirable, is a daunting technological challenge that must be addressed before seamless all-day personal position tracking can be made available.
Moreover, even when reliable GPS is available, its use may be minimized to preserve device power; battery life is an important monitored resource in most smart phones. This problem becomes more pronounced with respect to the use of GPS chips in even smaller devices such as wrist mounted smart-watches. The batteries in such devices often have capacities as low as 200 mAh; thus, if GPS were to be used continuously in such a device, the battery would be depleted within a few hours.
While there have been attempts to cure these problems, they have only been at most partially successful. For example, in order to circumvent the poor performance of GPS in indoor environments, the possibility of using additional technologies such as WiFi, cellular network, Ultra-Wideband radio, etc., to provide positioning information has been explored. However, no such solution effectively provides effective indoor position tracking, due to poor accuracy or the need for dedicated infrastructure.
While the present disclosure is directed to a system that may eliminate the shortcomings noted in this Background section, it should be appreciated that no such benefit is a necessary limitation on the scope of the disclosed principles or of the attached claims, except to the extent expressly recited in a claim. Additionally, the discussion of technology in this Background section is reflective of inventor observations or considerations, and is not intended to be admitted or assumed prior art as to the discussed details. Moreover, the identification of the desirability of a certain course of action is the inventors' observation, and should not be assumed to be an art-recognized desirability. The citation of references is not intended to provide a broad and inclusive summary of the references, and nothing in the foregoing is intended to conclusively characterize any reference. Rather, only the references themselves are art, and this section is expressly disclaimed as art, prior or otherwise.